Lance Armstrong finished among the leaders in the Tour of California's opening stage yesterday despite having to tackle drenching rain, a flat tire and even the theft of his time-trial bike.

Armstrong persevered to finish fifth in the stage, although he was awarded a finish time identical to that of 17 other riders in a large peloton directly behind the surprise winner, Francisco Mancebo of Spain.

Armstrong led a chase group that never quite caught up to the soaked race leaders on the final miles of a gruelling 107-mile grind.

But the day began inauspiciously and got worse before a solid finish by Armstrong, who might have been rethinking his comeback during five hours in the rain."Holy hell. That was terrible," Armstrong said afterwards. "Maybe one of the toughest days I've had on a bike, purely based on the conditions. I'm still freezing."

Team Astana, for whom Armstrong rides, lost four bikes to thieves Saturday night, including the American's time-trial bike which was stolen from the Astana truck in Sacramento along with the race bikes of team-mates Steve Morabito, Yaroslav Popovych and Janez Brajkovic.

Astana spokesman Philippe Maertens confirmed the bike thefts after it was reported by Armstrong himself on the Twitter website. The seven-time Tour de France winner later posted a picture of his missing bike, which has distinctive yellow-and-black wheels and the logo of his Livestrong foundation. "There is only one like it in the world therefore hard to pawn it off. Reward being offered," he wrote.

The rain fell in steady sheets from the opening miles of Stage 1 in Davis, a famously bike-friendly college town south-west of Sacramento. Most riders needed about five hours to cross the rolling hills of the Napa Valley before ending up in Sonoma County, but Armstrong stayed in contention despite a flat tire along the way.

Race officials did not release the stage's results until three hours after the leaders crossed the finish line, apparently debating how to handle the rulings made necessary by the rain. Armstrong and Astana teammate Levi Leipheimer, whose hometown is Santa Rosa, were among the 18 riders all given identical finish times 67 seconds behind Mancebo. Their individual finishes‚ Armstrong in fifth and Leipheimer in 15th, will count in the overall points standings.

The intricacies of the officials' decision didn't matter to Mancebo, an 11-year professional who joined Rock Racing this year. He took an early lead and stayed in front of the chase group until the downtown finish, when Vincenzo Nibali of Liquigas caught him with just one lap to go on the three-lap circuit.

Mancebo somehow reclaimed the lead and barely held off Nibali and Quickstep's Jurgen Van de Walle in a surprisingly entertaining finish under such awful weather conditions.

The Tour of California is Armstrong's first competitive appearance in his native country since beginning his comeback last month. He will not need his time-trial bike again until Friday in Solvang, where the race holds its second time trial. That segment is crucial to Astana's hopes of winning the overall team title, however.